American Empire?

The America of the latter half of the 20th century to the present has inevitably drawn comparisons to great empires of the past: the British Empire, Roman Empire, and others.  I've often struggled with whether America is indeed an empire, for the idea seems antithetical to those American values of freedom and liberty that we all hold so dear.  In his book Imperial Grunts, Robert Kaplan spends some time discussing his thoughts on empire:Imperialism is but a form of isolationism, in which the demand for absolute, undefiled security at home leads one to conquer the world, and in the process to become subject to all the world’s anxieties.  That is why empires arise at the fringes of consciousness, half in denial.  By the time an imperial reality becomes truly manifest, it is a sign that the apex of empire is at hand, with a gradual retreat more likely than fresh conquests.Kaplan is clearly on the side of viewing America as an empire.  Under his formulation, perhaps the fact of America's empire is still on the "fringes of consciousness."  He goes on to describe the impetus for the expansion of empire as necessity rather than glory, and that puts the American invasion of Iraq and Afghanistan in stark perspective.  We told ourselves we went in for necessity, but the result is still the expansion of American presence and influence around the world.Despite those arguments, the label of "empire" is only relevant in so far as it effects how we behave.  Perhaps by Kaplan's definition of empire, I'm willing to accept the application of the empire label to America.  My next question, though, would be so what?  Does that label change how we behave?  Or is it simply a method of historical analysis, a kind of 20/20 hindsight that doesn't affect events at the time?  There is no doubt that we are in the midst of the American era, but how long that era lasts may have much to do with how we take the empire label.  Do we brush aside allies as unnecessary, or do we make sure that our power makes everyone better off?  These are the truly existential questions America faces, empire label or not.